Dimorphos's trajectory was significantly altered by rebound from the DART
collision.
According to study released on Wednesday, the asteroid Dimorphos'
trajectory was changed more by dust and rock plumes that were thrown up from
its surface after NASA's DART probe collided with it than by the kinetic
impact alone.
During the Double Asteroid Redirection Test mission in October of last
year, scientists effectively modified the location of an astronomical
substance in space for the first time in history. To test whether it was
feasible to deviate an asteroid system from its initial orbit, a 610kg
(1,345lb) spacecraft was programmed to collide head-on with a pair of
asteroids.
DART achieved great achievement. Its trajectory was reduced by 33 minutes
as a result of the impact from the collision with Dimorphos; it now revolves
around its parent asteroid, Didymos, in less than 11 and a half hours. The
shift is much more pronounced than was anticipated.
Dimorphos's momentum was altered more by material released from its surface
during the encounter than by the impact of DART, according to analysis of
the experiment's data.
According to an article published in Nature, the ship alone would have
changed Dimorphos's orbit by seven minutes, but the recoil and ejecta
produced by the collision reduced it even more. According to a second
analysis, the asteroid's surface material loss added between 2.2 and 4.9 times to
the shift in momentum.
With enough time, warning, and resources, we can prevent an asteroid
impact,
according
to Derek Richardson, an astronomy professor at the University of Maryland
(UMD) and the working group leader for the DART investigation. "We can't
stop hurricanes or earthquakes yet, but we ultimately learned that we can
prevent an asteroid impact," he said. A comparatively minor shift in an
asteroid's orbit could, given enough time, cause it to miss the Earth and
avert widespread destruction of our world.
In order to allow space agencies enough time to prepare and carry out a
kinetic impact mission, astronomers would need to detect the object in
advance—"several years at a minimum, but ideally decades"—of their intended
impact.
Potential threats aren't always simple to detect before they're nearby,
despite numerous attempts being made to map near-Earth objects. For
instance, a truck-sized asteroid that was only found a week before it passed
a few thousand miles from Earth in January 2023 made one of the nearest
passes ever documented.
It is more difficult to divert an object the closest it is to striking the
Earth, Richardson told The Register. "Practically speaking, that implies
that we would require a larger ship (or more than one), moving more quickly,
and launched earlier than a threat further away. Therefore, the more alerts
we receive, the better. We are unable to specify a precise upper limit
because the size of the potentially dangerous item also plays a role. The
larger the object, the stronger the strike we would need to use, etc."
However, the success of DART "builds confidence about humanity's ability to
defend the Earth from an asteroid danger," experts
wrote
in a
third
article, which was also published in Nature. According to a fourth research,
the expelled material left Dimorphos with a comet-like tail, converting it
into a so-called "active" asteroid.
We still don't fully understand how Dimorphos and its progenitor asteroid
Didymos were affected by the impact. DART had only a camera and was
completely obliterated when it hit. In a follow-up journey in 2024, the
European Space Agency will send its Hera probe to conduct a more thorough
analysis of the binary asteroid system.
"The precise mass of Dimorphos is the [top] question the DART team wants
answered, according to Richardson. "We will be able to determine the
impact's effectiveness once we know that information combined with the
trajectory shift that was witnessed. But there are many other things we
would like to know, such as whether or not we created a crater that was so
large that it greatly altered the moon's general shape. Did we substantially
alter the moon's rotation?
"Is there any leftover material in the system's orbit? Did Didymos receive
a significant quantity of material that had a discernible impact on its
surface? What's Dimorphos' interior structure like—is it a pile of debris
from top to bottom or just on the surface? What can we infer about the
formation of asteroid moons and the long-term evolution of those
moons?"
Experts are developing new technologies that could be used to divert an
object in space as part of their efforts to improve planetary defense
strategies. According to UMD Principal Research Scientist Tony Farnham,
efforts are being made to identify possible targets for testing
asteroid-bumping devices in the future.
He informed us "Apophis will be investigated during its passing in 2029,
and preparations call for the OSIRIS-Rex spacecraft to be diverted in order
to converge on the asteroid. O-Rex will describe its physical
characteristics and investigate what transpires to the Apophis during the
pass of the Earth."
